1. Field of the Invention
The present invention generally relates to a method for inserting an absorber (hereunder sometimes referred to as a negative pressure producing material) into a case which accommodates the absorber. More particularly, the present invention relates to a method for inserting into an accommodating portion an absorber which is larger than the accommodating portion.
2 . Description of the Related Art
There has been developed a device into which a recording head and an ink tank are integrated for use as recording means in a small-sized ink jet recording apparatus. Further, such a device is detachably mounted on the apparatus to perform a recording operation. In the case of such a device, namely, an ink tank of the cartridge type into which a recording head and an ink tank are integrated, it is necessary to produce a predetermined negative pressure on the ink in the ink tank. A method for producing such a negative pressure is to insert an absorber into the ink tank and impregnate the absorber with ink.
For inserting absorbers into such an ink tank, a method of manually inserting preliminarily compressed absorbers thereinto one by one has been employed. Further, in this method, ink has been injected by an ink injector into the inserted absorbers. Manually inserting the absorbers in this manner takes much time and labor and is unsuitable for mass production. Moreover, unnecessary wrinkles have sometimes occurred in the absorbers when inserting them into the ink tank. Furthermore, occasionally a part of the absorber does not adhere closely to the inner surface of the ink tank. All in all, it is difficult to obtain consistent results when inserting the absorbers in accordance with this method.
When a wrinkle or a gap occurs in the absorber inserted in the ink tank as described above, a small pool of ink may be formed therein. Then, when a recording operation is performed, the ink collected in the small pool is not supplied to the recording head and thus is left in the ink tank. Further, such a pool of ink can obstruct ink flow, which results in degradation in the capability of supplying ink to the recording head. Moreover, sometimes ink is not normally discharged and printing quality may deteriorate.
To avoid an occurrence of such a state, a method of a jig to uniformly insert a compressed absorber into an ink tank has been developed. The absorber, which has been inserted into the ink tank after being uniformly compressed by the jig, does not cause the aforementioned small pool of ink. Accordingly, as ink is consumed by performing a printing operation, the ink in the uniformly compressed absorber is redistributed in the absorber. However, as the remaining quantity of ink in the absorber decreases, the negative pressure produced by the absorber increases. Thus, neither smooth movement nor sufficient supply of ink can be guaranteed. Moreover, the utilization ratio or efficiency of use of the in the uniformly compressed absorber tends to be low.
It is preferable for increasing the utilization efficiency of the ink in the absorber that the absorber compression gradually increase in inverse proportion to the distance from an ink supply opening of the recording head.
For example, U.S. Pat. No. 4,771,295 and No. 5,025,271 disclose that the capillary force of an absorber put into an ink tank is regulated in an ink jet cartridge in which a rib is provided in a portion thereof at an ink supply opening so as to regulate or increase the capillary force of the absorber at that location. Moreover, U.S. patent application Ser. No. 08/323,050 filed on Oct 14, 1994, now abandoned, discloses an absorber that has an enlarged shape that causes the absorber to be compressed when inserted in an ink tank so that the part of the absorber located in the vicinity of the ink supply opening is compressed in the proximity to the ink supply opening.
However, in the former method, variations in characteristics of mass-produced ink tanks may cause the efficiency of ink in such ink tanks to be unstable. In the latter method, when inserting the absorber into the ink tank, a wrinkle may occur in a region used to increase compressibility and the ink supply capability of the device thus may not be improved any way.
In any event, the aforementioned conventional absorber inserting methods may not suitably and accurately regulate the relation between (or the distribution of) dense and less-dense parts of the absorber inserted in the ink tank.